Both men were in their early 20s but lived a world apart. Hudner was the white son of a successful grocery store owner in Massachusetts, while Brown's father was a Mississippi sharecropper.

Thomas Hudner made a promise to the mortally wounded pilot Jesse Brown that he would come back for him.

Brown's F4U Corsair was damaged while flying near the Jangjin Reservoir, known as the Chosin Reservoir by Americans, in the northeast of North Korea. He crash landed on the rough snow-covered terrain.

Hudner refused to leave him.

He crashed his own plane close by with the intention of pulling Brown from the wreckage. But Brown's legs were trapped and Hudner was unable to free him. When a Marine helicopter landed to stage a rescue, Hudner had to make the agonizing decision to leave Brown.

"The Marine pilot pulled me aside," Hudner told CNN, "and said dusk was approaching and he couldn't fly the helicopter in the dark and the mountainous terrain, so he had to leave. But he said I had the option of going with him or to stay with Jesse, which would have been obvious suicide."

"I told Jesse that we had to get some more equipment because we couldn't get him out with what we had... I don't know if he even heard m. I'm afraid by this time he had passed."

The U.S. military decided to drop napalm on the wreckage so that Brown's body and the aircraft would not fall into enemy hands.

In a rare show of cooperation with a country it often calls the imperialistic enemy, North Korea has given permission for Hudner to return to Chosin Reservoir.

The Korean War broke out in June 1950 when communist North Korea attacked its southern neighbor. United Nations forces, made up primarily of U.S. personnel, fought on the side of South Korea. China fought with North Korea.

Choisin Reservoir was the scene of a harrowing battle waged during the brutal Korean winter, with frostbite a common injury. Arms and medical supplies also froze in subzero temperatures.

Of the 15,000 U.S. troops involved, more than 3,000 died during the 17-day struggle. But the Chinese forces paid a much greater price trying to force the allied troops from their positions -- some 60,000 replacements were required to replace men lost to firepower and cold. An estimated 35,000 Chinese troops lost their lives.

Hudner told CNN he didn't think the trip would ever happen.

"We're very grateful to him (leader Kim Jong Un) and to the North Korean government that after all these years we've been given permission to look for Jesse's airplane," he said.

He puts the chances of finding Brown's remains or his aircraft at 50-50, but says it is important.

He said severely strained US-North Korean relations could get a boost.

"Of course, that olive branch has to be extended and accepted by both sides," said Hudner. "There's an important factor that not many people talk about, but in World War II the Japanese and the Germans were our bitter enemies and now they're some of our closest friends."

An armistice agreement was signed on July 27, 1953, but a peace treaty has never been signed, meaning the two Koreas still are technically at war.

The 60th anniversary of the end of the war is just one week away and Pyongyang has planned a military parade and mass celebrations on what it calls "Victory Day." The group is not planning on attending the commemoration.

The timing of the invitation to the U.S. veterans is likely intentional, but for Hudner, the focus is bringing closure to his Korean War experiences and to Brown's family. Brown's widow and daughter, who was just a toddler when he died, are hopeful he will be found and eventually brought back home.

Almost 8,000 American military personnel are still missing in action in the conflict.